1. Field of the Invention
The present invention relates to a transport device for a system for finger jointing pieces of wood, having a support.
2. Prior Art
Such devices are usual for longitudinal gluing of rod-shaped pieces of wood, in other words for slats, boards, floorboards, and beams. In order to permanently connect the pieces of wood, the technique of finger jointing is used. For this purpose, the pieces of wood are sawed in corresponding finger jointing systems, at their ends, they are milled, then glued, and finally pressed together. These work steps can take place either in a single machine, or they can be functionally divided up among individual machines, depending on the system.
Two types of finger jointing systems are commonly in use: In individual processing, processing of the end face takes place with one piece of wood at a time. In packet-type processing, several pieces of wood are worked on at the same time, in order to increase the output, minimize splintering of the pieces of wood, and achieve precise glue application. In this connection, the pressing process always takes place in a separate press.
Among the packet systems, in turn, a differentiation is made between two different embodiments. In the case of a central packet system, only one central processing station is present for simultaneous or serial processing of two packets of wood, in each instance, on both sides of the machine. This is a tried and proven technique that has been in use for many years. However, the running meter output no longer meets today's requirements. For this reason, this type of system has been almost completely displaced by a second system type, in which a separate processing station is present per packet end, in each instance. In this connection, it is disadvantageous that because of the additional station, both a greater likelihood of breakdown and an additional space requirement occur.
In the case of all the system types mentioned, the transport of the pieces of wood in the longitudinal direction is carried out with conveyor belts or roller conveyors. Acceleration of the pieces of wood during transport takes place by way of adhesion friction between conveyor rollers, conveyor belt, and pieces of wood. The greatest possible acceleration values of the wood pieces are therefore limited by the low adhesion friction between them and the conveyor belt, thereby reducing the work speed of the system as a whole.
In the case of the conventional systems, alignment of the pieces of wood with regard to the packet end takes place in that the pieces of wood are conveyed lengthwise against a shaker stop. In this connection, the shaker stop pulsates in the transport direction, by about 1-5 cm, and thereby supports aligning of the pieces of wood.
In order to achieve uniform wood quality, the regions of the pieces of wood that have defects or irregularities such as knotholes are shortened by means of sawing. The lengths of wood within a wood packet can therefore demonstrate great differences, whereby the longest piece of wood can have a length up to ten times greater than that of the shortest piece of wood. The shorter pieces of wood must therefore move along the long pieces of wood during alignment, within the packet as a whole. It is a disadvantage, in this connection, that the friction between the pieces of wood hinders this relative movement.
While the longer pieces of wood are already at the shaker stop, and continue to be transported against the shaker stop when there are continuous rollers, the short pieces of wood are migrating in the direction of the stop. In this connection, the positions of the long pieces of wood, crosswise to the transport direction on the stop side, can change, and they therefore stand at a slant. Once the long pieces of wood have positioned themselves at a slant, additional forces that reinforce slanted positioning occur. As a result, and because of the adhesion friction between face ends of the pieces of wood and shaker plate, it is difficult or actually impossible to reposition them. Possible inaccuracies in the geometry of shaker plate and roller conveyor reinforce the tendency toward slanted positioning, in this connection.
Because of the slanted positioning, the pass-through path of the short pieces of wood between the long pieces of wood, or between the long pieces of wood and the side wall, is made narrower, so that the short pieces of wood do not pass through all the way to the end stop, and get stuck on the way.
It is true that some systems have an electronic system for recognizing when short pieces of wood have gotten stuck, and for eliminating the jam-up by means of various mechanical cycle movements. However, the electronics are complicated, on the one hand, and have a tendency to break down, on the other hand. Furthermore, not all problems are recognized. Even if it is possible to do so, manual intervention is generally required, and correcting these problems involves a time delay in the work sequence.